1. Field of the Invention
The present invention relates to a clutch disengagement and engagement apparatus, and more particularly to such an apparatus that can realize automatic operation of a vehicle clutch.
2. Description of the Related Art
Automatic clutch apparatuses for automatically disengaging and engaging a friction clutch are known in the art. With the automatic clutch apparatus, a clutch engagement speed is generally reduced in a partly engaged range in order to soften or eliminate shock which would otherwise be caused upon clutch engagement. However, the partly engaged range varies with wear and deformation of the clutch as well as assembly error. Therefore, it is necessary for the apparatus to repeatedly learn the partly engaged range of the clutch.
One of recent ways of learning the partly engaged range of the clutch is called "in-neutral learning method." This is a method of studying a "drag position" of the clutch (i.e., a clutch-stroke-position at which the clutch partly engaged range or condition starts)" when a transmission is in a neutral condition and therefore it is also referred to as "drag position" study method. This approach will briefly be described below.
1) The clutch is automatically brought into a complete disengagement position after predetermined study conditions such as a transmission gear position (shift position) being a neutral, a vehicle being in standstill, etc., are met. PA1 2) To wait until an output element (output shaft) of the clutch stops rotating. PA1 3) When the rotation of the clutch output element stops, the clutch is automatically engaged slowly. PA1 4) As the clutch engagement starts and the rotational speed of the clutch output element reaches a prescribed threshold value, then the clutch stroke position at that point is determined as the start of the partly engaged range. PA1 5) The clutch is automatically brought into a complete engaged condition.
In this manner, the clutch is disengaged and engaged when the clutch-stroke-position learning is performed.
In the meantime, a manual transmission is sometimes combined with the automatic clutch apparatus so that the gear position change of the transmission is carried out by a driver's hand whereas the clutch disengagement and engagement is carried out automatically. With such combination, transmission gear engagement and disengagement is possible for a certain period since the clutch is first disengaged during the clutch-stroke-position learning. If a driver manually moves a shift lever into a particular gear position and transmission gear engagement is effected, then the vehicle will start upon clutch engagement. In particular, if the driver inadvertently causes the transmission gear engagement, the vehicle will start without driver's intention. This is not preferred.
It is also known to automatically change the gear position of the manual transmission by an actuator. If this technique is combined with the automatic clutch apparatus, the shift lever simply serves as a switch. Therefore, if movements of the shift lever are ignored by the software of the automatic clutch apparatus during the clutch-stroke-position learning, the above-described problem will easily be overcome. However, if the driver manually changes the gear position of the manual transmission by a mechanical device, the movements of the shift lever directly result in gear engagement and disengagement of the transmission gears. Thus, it is not possible to overcome the above-mentioned problem by the software design.
Other systems and methods for disengaging and engaging a clutch are disclosed in U.S. patent application Ser. Nos. 08/967,401 filed Nov. 11, 1997, Ser. No. 09/150,686 filed Sep. 10, 1998 and Ser. No. 09/207,180 filed Dec. 8, 1998, and International Patent Application No. PCT/JP98/02754 filed Jun. 19, 1998, all of which are entirely or partly assigned to the assignee of the instant application.